A movable robot has a member linearly movable in the horizontal direction and an arm mounted on the movable member and vertically movable upwardly and downwardly. More particularly, a robot controller for such a robot plays back the points of a stored welding program by interpolating the position of the movable member as well as the position and the attitude of the arm.
The present invention relates to improvements in a robot controller for simultaneously playing back the prestored motions of an arm and an upright movable member of a movable robot.
In the playback operation of prior-art movable robots of this type, the control of an arm and the control of a movable member are independent, and the motions of the arm and the movable member of the robot are not simultaneously controlled. In other words, in prior-art robots, the movable member is first moved to and stopped at a predetermined position to be welded, the position of the arm is then interpolated, the movable member is thereafter moved and stopped again at another welding position, the arm position is again interpolated, and another welding operation is performed. In summary, prior-art robots operate for only discontinuous weldings.
However, when a considerable welding task is required on a workpiece, for example, when the weld required is long in length, the positioning of the movable member and the interpolation of the arm position are individually performed in prior-art movable robots. This is not only very troublesome, but also time consuming. Thus, prior-art robots have such drawbacks that the robot cannot simultaneously move its various articulated members and thus is restricted in the possible working range to the movable range of the arm.